for trashbot 6 i planned to change the arduino nano into a raspberry pi 2. i also moved the board below the hips as luckily, the three mgr 996 servos of the hip are as wide as the raspberry pi:

but as you can see on the lower left (where the edimax wifi plug is inserted), the usb ports are pretty much flush with the outer servos, i.e. the attached legs will not leave too much space for usb plugs. Continue reading →

I always love to obey to minimalism and I always love to construct stuff with a minimal amount of material and complexity. Of course, the question is then how replicable, durable and maintainable the result is.

In the present case it became obvious, that at some point in time, Trashbot would need to have an additional degree of freedom on his foot, namely an ankle that allows him to lean forward. The present prototype is acutally from August last year. But now I’m revisiting my designs as Trashbot recently got the long awaited additional hip servos and the logical next step is to add the ankle servos.

Last week I added three degrees more to Trashbot, two hip servos for forward movement (“kicking”) and one to the bone.

This week I found some time to do the first single servo movements and tests to check out the new geometry of the bot since the broader hips will affect the Center of Gravity etc. Here’s the first attempt to do what the normal gait would do: shift the body to one foot:

I’ve been working on Trashbot for quite a while now, but the basic gait mechanism is still the same as in version one. The hips’ movements and the distance between the legs define the possible step length. This is annoying since the robot is rather tall and you’d expect that he’ll walk a bit faster than he actually does. However, moving faster induces stronger vibrations in the skeleton and makes him fall much easier.

this time it took really long to make more progress on trashbot but i had the feeling that there were many little improvements that made the bot better and somehow it felt like none of them were big enough to be worth a post.

now in the end i learn that quite a lot happened during the last 8 or so weeks and over easter i invested some time also into the cleanup of the software.

first of all, i added shins to the legs so that he wouldn’t swing too much when shifting his weight from one foot to the other. i used some screw / hooks that you use to hang wired lamps and have a tension on the wires:

recently, i had the idea to attach a laser pointer to trashbot’s neck and investigate the amplitudes of the laser on the ceiling. this time, the blog entry is shorter but the “how-to” is in the video:

from the results you can see much better the difference between active balancing:

vs no balancing (the spine is stiff, the upper body moves with the hip, thus larger amplitudes):

with this technique, i hope to be able to document further improvements on the movement, especially when i connect the gait pattern with the balancing mechanisms as scientific robots do.

i recently contrasted trashbot 3’s walk with the spine balancing or bein static and was not happy with the result of the video. one can have the impression that active vs non-active balancing is somewhat similar but in fact the real robot “feels” different as we’ve seen in the video above.

next, i’ll attach a little camera (gopro clone) to the trashbot’s chest to view the gait from “first person” perspective…